An X‐Ray Search for Compact Central Sources in Supernova Remnants. II. Six Large‐Diameter SNRs

We present the second in a series of results in which we have searched forundiscovered neutron stars in supernova remnants (SNRs). This paper deals withthe largest six SNRs in our sample, too large for Chandra or XMM-Newton tocover in a single pointing. These SNRs are nearby, with typical distances of <1kpc. We therefore used the ROSAT Bright Source Catalog and past observations inthe literature to identify X-ray point sources in and near the SNRs. Out of 54sources, we were immediately able to identify optical/IR counterparts to 41from existing data. We obtained Chandra snap-shot images of the remaining 13sources. Of these, 10 were point sources with readily identified counterparts,two were extended, and one was not detected in the Chandra observation but islikely a flare star. One of the extended sources may be a pulsar wind nebula,but if so it is probably not associated with the nearby SNR. We are then leftwith no identified neutron stars in these six SNRs down to luminosity limits of\~1e32 ergs/s. These limits are generally less than the luminosities of typicalneutron stars of the same ages, but are compatible with some lower-luminositysources such as the neutron stars in the SNRs CTA 1 and IC 443.Comment: 32 pages, 30 figures; uses emulateapj.cls and hyperref.sty. Accepted for publication in ApJ